I studied John Ford and the Western genre for Film Studies way back in my college days, so never really got on with his movies after that!
I concur with Leone's 'Once Upon a Time in the West', his masterpiece (and if you're really interested in what I think of it, I wrote an in-depth review of that here - https://medium.com/p/5cf5f2274473) but prefer his dollar trilogy, for their mythic qualities.
As it happens, I also wrote about 'The Great Silence' (thanks for commenting on that review, BTW) and, woah, is that a bleak one in every respect!
Oh and 'High Noon' also - https://medium.com/p/641e92fffede - so our tastes certainly overlap a great deal... (I can't remember ever seeing 'The Naked Spur', so thanks for the prompt.)
I must admit, the Western is not one of my 'go-to' genres, and I think there has to be some genre-bending for me, and some of those you list fall into that category (eg, Wild Bunch / Great Silence). Generally, though, I only really enjoy Euro-westerns... perhaps the Americans are trying too hard to revise their own history to have much fun with the tropes?
Thanks and keep up the great work!